This invention relates to the indication of changes in a desired operating condition and, more particularly, to the indication of when a motor is operating at, above or below a desired speed.
The operating condition of a device is frequently represented by a signal which is compared with a reference to provide a measure of the departure of the signal from a desired condition.
Such an arrangement has the disadvantages of requiring a precision reference source. It also requires a precision, high gain comparitor that typically acts either on frequency or amplitude levels.
Accordingly it is an object of the invention to provide a suitable indicator for changes in a specified operating condition.
Another object is to provide a suitable indicator for departures from a desired motor speed condition.
A further object is to provide an indicator which does not require a precision reference source, or a precision comparitor for frequency or amplitude level.